Miles per gallon meter



D ec. 26, 1961 Filed Jan. 2l, 1959 S. F. FAUNCE MILES PER GALLON METER 2 Sheets-Sheet 1 INVENTOR T2/P7- EFqa/vcze;

ATTORNEY Dec. 26, 1961 l s. F. FAuNcE 3,014,366

MILES PER GALLON METER Filed Jan. 21, 1959 2 Sheets-Sheet 2 @Y6/NE ATTORNEY 3,014,366 MILES PER GALILN METIER Stuart F. Faunce, 169 Paterson Road, Fanwood, NJ. Fried Jan. 21, 195s, ser. No. 783,@79 6 Claims. (Cl. 73-134) This invention relates to a milles per gallon meter as a means of providing performance information to the operator of an engine, particularly automotive engines as when employed on autovehicles, automobiles, buses, trucks diesel locomotives, motor boats, etc.

The primary object of the invention is to provide a dash-type mounted instrument which reads in miles per gallon and that will be of value to the average layman who has had no technical training and `who can install it easily himself. In order to meet the objective above, there are certain characteristics that the device must meet, such as low cost, simple and rugged, and react very quickly (with no noticeable delay) in changes of power as encountered by fast acceleration or hills. In

order to illustrate these characteristics it is necessary to v discuss the fuel and power system, and to point out why this invention meets these conditions and therefore is an improvement over the methods and means described in the prior patent literature.

In all of the previous patents encountered describing the efficiency devices, either meters or some type of sensing ele-ment (such as heated wires) have been placed in the liquid line ahead of the carburetor. Consider now the actual liquid fuel system into and through the carburetor, i.e.,.the carburetor, see FIG. 4, has a lloat and associated fuel chamber which is in effect a reservoir. The metering of the fuel in the carburetor which includes the main fuel jets, accelerator pump, and power'stroke into the air stream is all immediately downstream of the reservoir. The inlet to the reservoir is a valve operated by the float. Thus, as an example, consider a very quick acceleration where the fuel must come from the accelerator pump cylinder, then from the reservoir and then from the fuel line and the-evidence indicates a time lag must occur. In a modern conventional carburetor, the reservoir liquid surface area to the cross-sectional area of the supply fuel line has a ratio of 17.5 to 1. This ratio indicates that in rapid liuxations o-f power the `fuel iiow in the line will be subject to a time lag, and thus produce erratic values of the fuel flow which in turn will be translated into the meter movement.

In order to eliminate the diiculty of the time lag just mentioned and to have suilicient power to activate a fuel measuring device, and at the same time making it possible to provide a low-cost system which can be installed by the average layman, the gas ow is used to arrive at the fuel ow. 'For an example of usingV the gas flow the following comments based on the exhausty gas are given. The validity and justification of using the exhaust gas flow can be seen by the use of a mass vbalance of the combustion components in which the weight of fuel plus weight of air for combustion must equal the 'weight of the exhaust'gas products. First, it is necessary to sayV that the variation of the hydrogen to carbon ratio i of fuels and the fuel-air ratio of the carburetor is within proper limits so that a miles per lgallon meter of suicient accuracy can be built. Next, because four-fifths of the air is nitrogen which -remains'unchanged as it passes through the engine, there is little variation in the molecular weight of the exhaust gas due to variations in the combustion process. As a result of the limits of variation in the actual combustion process and the ability to calibrate the flow conditions Ufor a givenexhaust geometry, one can establish the fuel flow by measuring the exhaust gas flow. The exhaust gas flow is then determined by placing a pressure tap in theV exhaust system at an approtllllh Patented Dec.. 26, 1961 priate and calibrated location so that the pressure actuates a displacement surface which in turn moves a contact along a wire which is a variable resistance in an electrical circuit. The muiiler and tailpipe can serve as the resistance to fluid iiow for the action is analogous to that of an orifice in that the pressure variations are indicative of the rate of exhaust gas flow. FIGURE ll illustrates the pressure tap location in relation to the mufer and tailpipe section. This variable resistor has been built so that the displacement of the contact due to the exhaust gas pressure gives a resistance value that is proportional to the fuel flow.

The D.C. generator with its permanent magnets is completely separate of any exterior powerl source so that its output is directly proportional to and only influenced by the cars speed. Since the variable resistor unit has been built and calibrated so that the resistance is directly proportional to the fuel :tlow and using the electrical analogy of the voltage representing car speed and the resistance representing fuel flow, then the circuit current represents miles per gallon. Of course, it must be realized that appropriate conversion factors must be established between the electrical analogue and the car speed, fuel ilow, and miles per gallon system.

With these and other objects in View, the invention consists in the novel details of construction and combinations of components more fully hereinafter disclosed and particularly pointed out in the claims.

Referring to the accompanying drawings, in which:

FIG. l is a schematic arrangement of the miles per gallon meter components and illustrate how they tit into an automobile speedometer and fuel system.

FIG. 2 is an electrical wiring diagram showing the circuit relationship of the generator, milli-ammeter, and variable resistor of the system of FIG. 1.

FIG. 3 is a half-sectioned view illustrating the details of the fuel pressure transducer of FIG. 1.

FIG. 4 is a fragmentary section of FIG. 1 which shows a schematic arrangement of the main components of a carburetor. This sketch shows how the throttle valve controls the air ilow which in turn controls the fuel ow.

FIG. 5 is a fragmentary View of FIG. 1 which shows the pressure tap 1 connected to the intake manifold of the engine. i

FIG. 6 is a fragmentary view of FIGS. l and 4 which shows the pressure tap 1 connected to the venturi section of FIG. 4.

FIG. 7 shows a fluid ow meter with an open end instead of a closed end with a val-ve as illustrated in FIG. 3.

Referring to FIG. 1, reference number 1 shows the pressure transmitting tube which transmits the pressure of the exhaust gas in the exhaust pipe 2 to the elastic displacement member 3 shown in FIGURE 3 which is deflected and moves rod 4 to which is fastened a spring 5 that has a contact point 6 which moves along the resistance wire 7. The resistance wire 7 is wound on a surface Sshown in FIGURE 3 which contains a slot along which the contact point 6 travels. The fluid pressure transducer t5 illustrated in FIGS. 3 and 7 has a finite 'length and an endless surface in that it may be a cylinder, an ellipse, or a polygon when viewed along its axis. Member 9 is a solid, rigid member having Van aperture to which tube 1 is fastened. Member 10 is a perforated dish-shaped member which serves as a guide for rod 4 as well as a stop for the diaphragm 3, in order to prevent it from being over stressed and damaged in case of a sudden surge of pressure. Member 11 is a rigid member which serves as a support for the surface ,S and a guide for rod 4 and spring 5.

Referring to FIGS. l and 2, the generator 12 is connected to the speedometer cable 13 with one electrical lead 14 connected to the fuel llow meter 15 and the other electrical lead 16 connected to the miles per gallon meter or indicator 17 which is connected to the fuel pressure transducer 1S by lead 1S.

Referring to FIG. l, the pressure tap 1 is shown attached to the exhaust gas system which contains the exhaust pipe 2, muffler 19, and tail-pipe 20. FIG. 5 shows the pressure tap 1 connected to the intake manifold 21 of the engine 22. 1ElG. 6 shows the pressure tap 1 connected to the venturi section 23 of the carburetor 24.

For an illustration as to how the system operates and that the time lag due to any changes in the speed or fuel flow is not noticeable in the miles p-er gallon meter consider the following:

First, the rotation of the generator armature 12 which is connected to t'ne speedometer cable 13 is directly proportional to the speed of the automobile and therefore the generated voltage is directly proportional to the automobile speed.

Second, the working medium of the power system is the air to which the fuel supplies energy as, in general, there are 15 pounds of air required for every pound of fuel, and the throttle valve of the carburetor controls the ow of air, and it is the tiow of air through the carburetor which determines the ow of fuel. A sudden change in the throttle valve position caused by the operators foot on the accelerator pedal will cause a sudden change in the air flow which will cause a change in the flow of fuel from the carburetor reservoir, but not necessarily from the fuel line. Since the velocity of the exhaust gas in the tail-pipe 2G varies from about 25 to 200 ft./sec., the time between any change in the position of the accelerator pedal and the resistor contact point 6 will always be less than about one-half second. As previously stated, the variable resistance mechanism, FIG. 3, is built so that the resistance 7 of FIG. 2 is directly proportional to the fuel llow, so that there is no noticeable lag 4between the resistance value of FIG. 2 and the fuel flow.

Third, the voltage and the resistance of the circuit of FIG. 2 is directly proportional to the automobile speed and fuel ilow respectively, so that the current therefore is proportional to the car speed divided by the fuel flow as given by the equation E K V f T- where G==gallons per hour I amps. E :voltage RT=tota1 circuit resistance K=constant with value of amps. per mile per gallon V=speed in miles per hour 4 described here is an improvement in that the components used are conventional, the electrical circuit is simpler, the time lag which is encountered in the measurement of the ow of the liquid fuel is eliminated, and the overall simplicity makes it possible to meet the primary objective previously stated of making the unit of value to the average automobile operator.

It is readily understood that the details of this device may be changed without departing from the spirit of the invention, therefore, I wish not to be limited otherwise than is indicated by the following claims.

What is claimed is:

1. In a system for indicating the mileage per gallon of fuel of a vehicle, an electric generator whose output is proportional to the speed of the vehicle, a pressure transducer having an electric resistance element whose resistance instantaneously indicates the fuel flow of the vehicle, an ammeter calibrated to indicate the mileage per gallon of fuel consumed by the vehicle, a closed circuit connecting the generator, the ainmeter and the resistance element in series, and a tube connecting the pressure transducer to the exhaust pipe of the vehicle, the tube connection being located at a point in the exhaust pipe which has a known calibration of fuel flow versus fluid pressure, the fluid pressure producing an instantaneous variation in the resistance of the circuit.

2. A system for indicating the mileage per gallon of a vehicle as indicated in claim l in which the electric generator is driven by the speedometer cable of the ehicle.

3. A system for indicating the mileage per gallon of a vehicle as indicated in claim 1 in which the tube connection to the exhaust pipe is located immediately ahead of the mufller of the vehicle.

4. In a system for indicating the distance traveled per unit of fuel consumed by a vehicle, a source of electric current the output of which is proportional to the speed of the vehicle, a pressure transducer having an electric resistance element which instantaneously indicates the fuel ilow of the vehicle, an ammeter calibrated to indicate the distance traveled per unit of fuel consumed by the vehicle, a closed circuit connecting the current source, the ammeter and the resistance element in series and a tube connecting the pressure transducer to the exhaust pipe of the vehicle, the tube connection to the exhaust pipe being located at a point which has a known calibration of fuel flow versus fluid pressure, the tluid pressure producing an instantaneous variation in the resistance of the circuit.

5. A system for indicating the distance traveled per unit of fuel consumed by a vehicle as indicated in claim 4 in which the electric generator is driven by the speedometer cable of the vehicle.

6. A system for indicating the distance traveled per unit of fuel consumed by a vehicle as indicated in claim 4 in which the tube connection to the exhaust pipe is located immediately ahead of the muffler of the vehicle.

References Cited in the tile of this patent UNITED STATES PATENTS 1,811,769 Weaver June 23, 1931 2,304,822 Harrison et al Dec. 15, 1942 2,454,393 Leonard Nov. 23, 1948 2,466,071 Barnes et al. Apr. 5, 1949 2,466,846 Giesler Apr. l2, 1949 2,621,513 Zschokke et al. Dec. 16, 1952 

